BIOLOGY IN FOCUS
MAINTAINING A BALANCE
Chapter 1 Temperature regulation
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Student Worksheet: The role of the nervous
system in the stimulus–response pathway for
temperature regulation
Task
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Linked to
page 19
The annotations in each of the boxes below summarise the steps in the process of
temperature regulation; however, the steps are not in order. Students should cut
out the annotations and match them to the sequence of diagrams illustrating the
stimulus–response pathway overleaf.
Functioning of the nervous system
Muscles or glands receive impulses
(via motor nerves) from the CNS; these
impulses instruct the effectors to bring
about a response—for example, sweat
glands produce sweat to cool the body.
Any change in the environment that can
be detected by receptors and triggers a
response (e.g. extreme heat) is termed
a stimulus.
Motor nerves carry information (as nerve
impulses) from the CNS to the effectors.
The central nervous system (CNS),
made up of the brain and spinal cord,
processes the information about the
change in external environment.
Information from particular receptors is
interpreted in specific parts of the brain.
The hypothalamus processes
information about body temperature
(as well as hunger and thirst).
Thermoreceptors in the skin and in
the hypothalamus of the brain detect the
stimulus (change in temperature) and
convert this into a ‘message’ in the form
of nerve impulses, which travel along
nerves towards the central nervous system
(brain and spinal cord).
A change within the body as a result
of a stimulus is termed a response—for
example, a cooling mechanism to
overcome excessive heat. The response
usually counteracts the original change
in external conditions to correct any
deviation, ensuring homeostasis. In
most cases, the response decreases the
effects of the stimulus: this is known as
a negative feedback mechanism.
1
Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.
BIOLOGY IN FOCUS
Stimulus–response pathway
Stimulus
sun
Receptor
brain
temperatureregulating centre in
the hypothalamus
Control
centre
spinal cord
anterior part of central nervous system
Messenger
neurons
evaporation
water
vapour
sweat
droplet
hair
heat
pain
receptors
sweat pore
epidermis
Effector
sweat
duct
sweat
gland
Response
2
Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.
BIOLOGY IN FOCUS
Additional information: sensory receptors in mammals
Electroreceptors are able to respond to electrical energy and they are found in
aquatic organisms such as fish, including eels, sharks and rays. Electroreceptors
are absent in most terrestrial animals and this is thought to be because air is such
a poor conductor of electricity, compared with water. The bill of a duck-billed
platypus contains electroreceptors.
3
Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.
BIOLOGY IN FOCUS
Answer
Stimulus–
response
pathway
Diagram
Functioning of the nervous system
Stimulus
Any change in the environment that can be detected by
receptors and triggers a response (e.g. extreme heat) is
termed a stimulus.
sun
Receptor
brain
temperatureregulating centre in
the hypothalamus
Control centre
spinal cord
Messenger
anterior part of central nervous system
Thermoreceptors in the skin and in the hypothalamus of
the brain detect the stimulus (change in temperature) and
convert this into a ‘message’ in the form of nerve impulses,
which travel along nerves towards the central nervous system
(brain and spinal cord).
The central nervous system (CNS), made up of the brain
and spinal cord, processes the information about the change
in external environment. Information from particular receptors
is interpreted in specific parts of the brain.
The hypothalamus processes information about body
temperature (as well as hunger and thirst).
Motor nerves carry information (as nerve impulses) from the
CNS to the effectors.
neurons
Effector
evaporation
water
vapour
sweat
droplet
hair
heat
pain
receptors
Muscles or glands receive impulses (via motor nerves) from
the CNS; these impulses instruct the effectors to bring about
a response—for example, sweat glands produce sweat to cool
the body.
sweat pore
epidermis
sweat
duct
sweat
gland
increased heat loss
Response
A change within the body as a result of a stimulus is
termed a response—for example, a cooling mechanism to
overcome excessive heat. The response usually counteracts
the original change in external conditions to correct any
deviation, ensuring homeostasis. In most cases, the response
decreases the effects of the stimulus: this is known as
a negative feedback mechanism.
4
Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.